Development of an All-Fiber Coherent Laser Radar for Precision Range and Velocity Measurements

An all-fiber coherent laser radar system capable of high-resolution range and line of sight velocity measurements is under development with a goal to aid NASA's new Space Exploration initiative for manned and robotic missions to the Moon and Mars. Precision range and velocity data are key parameters to navigating planetary landing pods to the pre-selected site and achieving autonomous safe soft-landing. By employing a combination of optical heterodyne and linear frequency modulation techniques [1-3] and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed.The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to directly measure the platform velocity by extracting the Doppler shift generated by the platform motion. The Doppler velocity measurement is about two orders of magnitude more accurate than the velocity estimates obtained by laser altimeters using the rate of change in range [4]. Another advantage is continuous-wave operation that allows the use of highly efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper will describe the design and operation of this laser radar sensor and discuss its projected performance. A laboratory breadboard system has already been developed as a step toward a flight prototype. The experimental data representing the potentials of this laser radar system will be reported.